The present invention relates to a system that provides navigation-related features to end users throughout a geographic region. More particularly, the present invention relates to a system that includes a centrally-located server that provides geographic data to end users' mobile units located throughout a serviced geographic region based on requests from the end users' mobile units.
Navigation systems provide various useful features, such as calculating routes to desired destinations, providing guidance for following calculated routes, displaying maps, and so on. There are various computer architectures for navigation systems that deliver navigation-related and map-related features. In one type of architecture for a navigation system, end users (such as vehicle drivers) have local mobile units that obtain geographic data from a remotely located geographic database and server. The remotely located geographic database contains a relatively large amount of geographic data. The server associated with the remotely located geographic database handles requests for navigation-related or map-related data from end users' local mobile units. When an end user's local mobile unit requests data, the server accesses the geographic database associated therewith to obtain the necessary data to respond to the request and then sends the data to the requesting end user's local mobile unit.
This type of navigation system architecture provides several advantages. One advantage relates to providing updated geographic data. There is a continuing need to update the geographic data used by navigation systems to reflect changes in the represented features. For example, new streets are built, road construction closes roads, detours are established, new businesses open, posted speed limits change, new turn restrictions are established at intersections, streets are renamed, and so on. These kinds of changes can affect travel through a geographic region. Accordingly, the geographic data used by a navigation system should be updated on a regular basis in order to accurately reflect changes in the represented geographic features. An architecture in which individual local navigation units obtain geographic data from a single geographic database affords an advantage with respect to the updating of the geographic data. With this type of system, updates need to be applied only to the central database.
Although there are advantages associated with a navigation system architecture in which individual local navigation units obtain data from a single geographic database associated with a central server, there are considerations that need to be addressed. One consideration relates to providing data to a large number of end users in a timely and efficient manner. Another consideration is that a relatively large amount of data may need to be transmitted to each user in order to provide features such as route calculation, route guidance and map display. This is especially the case if a sufficient amount of data representing features located in the vicinity of the user and along a route is provided to assist the user if he/she deviates from the calculated route. Thus, an efficient way is needed to transmit geographic data from a remotely located server to end users' mobile navigation units.